From 66c03577e02e91ebfa4a212bcd1723e473c6555d Mon Sep 17 00:00:00 2001
From: Gordon Williams <gw@pur3.co.uk>
Date: Tue, 17 Sep 2024 10:57:58 +0100
Subject: [PATCH] Graphics: allow arraybuffer graphics to be instantiated with
 an ArrayBuffer (rather than it always allocating one)

---
 libs/graphics/jswrap_graphics.c | 13 +++++++++++--
 libs/graphics/lcd_arraybuffer.c | 10 +++++++---
 libs/graphics/lcd_arraybuffer.h |  2 +-
 libs/hexbadge/jswrap_hexbadge.c |  2 +-
 libs/pixljs/jswrap_pixljs.c     |  2 +-
 5 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/libs/graphics/jswrap_graphics.c b/libs/graphics/jswrap_graphics.c
index da4fa4b2d..784bf3abc 100644
--- a/libs/graphics/jswrap_graphics.c
+++ b/libs/graphics/jswrap_graphics.c
@@ -603,7 +603,8 @@ static bool isValidBPP(int bpp) {
       "`vertical_byte` = whether to align bits in a byte vertically or not",
       "`msb` = when bits<8, store pixels most significant bit first, when bits>8, store most significant byte first",
       "`interleavex` = Pixels 0,2,4,etc are from the top half of the image, 1,3,5,etc from the bottom half. Used for P3 LED panels.",
-      "`color_order` = re-orders the colour values that are supplied via setColor"
+      "`color_order` = re-orders the colour values that are supplied via setColor",
+      "`buffer` = if specified, createArrayBuffer won't create a new buffer but will use the given one"
     ]]
   ],
   "return" : ["JsVar","The new Graphics object"],
@@ -632,6 +633,7 @@ JsVar *jswrap_graphics_createArrayBuffer(int width, int height, int bpp, JsVar *
   gfx.data.flags = JSGRAPHICSFLAGS_NONE;
   gfx.graphicsVar = parent;
 
+  JsVar *optionalBuffer = 0;
   if (jsvIsObject(options)) {
     if (jsvObjectGetBoolChild(options, "zigzag"))
       gfx.data.flags = (JsGraphicsFlags)(gfx.data.flags | JSGRAPHICSFLAGS_ARRAYBUFFER_ZIGZAG);
@@ -668,9 +670,16 @@ JsVar *jswrap_graphics_createArrayBuffer(int width, int height, int bpp, JsVar *
         jsWarn("color_order must be 3 characters");
       jsvUnLock(colorv);
     }
+    optionalBuffer = jsvObjectGetChildIfExists(options, "buffer");
+    if (optionalBuffer && !jsvIsArrayBuffer(optionalBuffer)) {
+      jsExceptionHere(JSET_ERROR, "'buffer' should be ArrayBuffer, got %t", optionalBuffer);
+      jsvUnLock(optionalBuffer);
+      return 0;
+    }
   }
 
-  lcdInit_ArrayBuffer(&gfx);
+  lcdInit_ArrayBuffer(&gfx, optionalBuffer);
+  jsvUnLock(optionalBuffer);
   graphicsSetVarInitial(&gfx);
   return parent;
 }
diff --git a/libs/graphics/lcd_arraybuffer.c b/libs/graphics/lcd_arraybuffer.c
index 5399aabc2..3526e108e 100644
--- a/libs/graphics/lcd_arraybuffer.c
+++ b/libs/graphics/lcd_arraybuffer.c
@@ -315,10 +315,14 @@ void lcdScroll_ArrayBuffer_flat8(JsGraphics *gfx, int xdir, int ydir, int x1, in
 
 
 
-void lcdInit_ArrayBuffer(JsGraphics *gfx) {
+void lcdInit_ArrayBuffer(JsGraphics *gfx, JsVar *optionalBuffer) {
   // create buffer
-  JsVar *buf = jswrap_arraybuffer_constructor((int)graphicsGetMemoryRequired(gfx));
-  jsvAddNamedChildAndUnLock(gfx->graphicsVar, buf, "buffer");
+  if (optionalBuffer) {
+    jsvAddNamedChild(gfx->graphicsVar, optionalBuffer, "buffer");
+  } else {
+    JsVar *buf = jswrap_arraybuffer_constructor((int)graphicsGetMemoryRequired(gfx));
+    jsvAddNamedChildAndUnLock(gfx->graphicsVar, buf, "buffer");
+  }
 }
 
 void lcdSetCallbacks_ArrayBuffer(JsGraphics *gfx) {
diff --git a/libs/graphics/lcd_arraybuffer.h b/libs/graphics/lcd_arraybuffer.h
index f330c04f7..9dc961485 100644
--- a/libs/graphics/lcd_arraybuffer.h
+++ b/libs/graphics/lcd_arraybuffer.h
@@ -13,7 +13,7 @@
  */
 #include "graphics.h"
 
-void lcdInit_ArrayBuffer(JsGraphics *gfx);
+void lcdInit_ArrayBuffer(JsGraphics *gfx, JsVar *optionalBuffer);
 void lcdSetCallbacks_ArrayBuffer(JsGraphics *gfx);
 
 // these use gfx->backendData as a pointer to data. They're exported so lcd_st7789_8bit can use them for fast offscreen rendering
diff --git a/libs/hexbadge/jswrap_hexbadge.c b/libs/hexbadge/jswrap_hexbadge.c
index cf69fab43..b4d008274 100644
--- a/libs/hexbadge/jswrap_hexbadge.c
+++ b/libs/hexbadge/jswrap_hexbadge.c
@@ -280,7 +280,7 @@ void jswrap_badge_init() {
   gfx.data.type = JSGRAPHICSTYPE_ARRAYBUFFER;
   gfx.data.flags = JSGRAPHICSFLAGS_ARRAYBUFFER_VERTICAL_BYTE | JSGRAPHICSFLAGS_INVERT_X;
   gfx.graphicsVar = graphics;
-  lcdInit_ArrayBuffer(&gfx);
+  lcdInit_ArrayBuffer(&gfx, NULL);
   graphicsSetVarInitial(&gfx);
   jsvObjectSetChild(execInfo.root,"g",graphics);
   // Set initial image
diff --git a/libs/pixljs/jswrap_pixljs.c b/libs/pixljs/jswrap_pixljs.c
index 0baec5ca7..3f7f6bf54 100644
--- a/libs/pixljs/jswrap_pixljs.c
+++ b/libs/pixljs/jswrap_pixljs.c
@@ -364,7 +364,7 @@ void jswrap_pixljs_init() {
   gfx.data.type = JSGRAPHICSTYPE_ARRAYBUFFER;
   gfx.data.flags = JSGRAPHICSFLAGS_ARRAYBUFFER_MSB;
   gfx.graphicsVar = graphics;
-  lcdInit_ArrayBuffer(&gfx);
+  lcdInit_ArrayBuffer(&gfx, NULL);
   graphicsSetVarInitial(&gfx);
   jsvObjectSetChild(execInfo.root, "g", graphics);
   jsvObjectSetChild(execInfo.hiddenRoot, JS_GRAPHICS_VAR, graphics);